A switching power supply such as a DC-DC converter is a power supply which has high efficiency and is suitable for reducing power consumption and size, and is used as, for example, a lighting circuit in a luminaire. In such a switching power supply, for example, a rising-falling type structure capable of raising and reducing voltage can be used also in a case where an input voltage and an output voltage are close to each other.
In recent years, as an illumination light source in the luminaire, an incandescent lamp or a fluorescent lamp is being replaced with an energy-saving and long-life light source, for example, a light-emitting diode (LED). Besides, a new illumination light source such as, for example, an electro-luminescence (EL) or organic light-emitting diode (OLED) is also developed. Thus, the lighting circuit for lighting the illumination light source is also required to have higher efficiency.